Week 2 - Diffie-Hellman Key Exchange

Question 1

What is the purpose of Diffe-Hellman Key exchange?

Answer 1

to generate a shared key over an insecure network allowing future secure communication

Question 2

How does Diffie-Hellman Key work?

Answer 2

1. a large prime number p and a base g are agreed
2. Alice and Bob each have a private key
3. A = g^a mod p
   B = g^b mod p
4. Alice send A to bob and Bob sends B to Alice
5. Alice secret key = B^a mod p
   Bob secret Key = A^b mod p
6. Alice key == Bob key

Question 3

Why is the Diffie-Hellman key exchange secure against attackers?

Answer 3

Attacker needs a or b to solve for the key, but these are private